some actually announce to the rest of the Internet all the routes that exist in
your network. Ingress traffic filtering is a condition in which an ISP accepts
only packets with a source address in an administrative range that belongs to
one of the ISP's customers. If all the ISPs on the Internet filtered using ingress
filtering based on source addresses, the Internet as a whole would gain con-
siderable immunity to malicious hackers' denial-of-service attacks.
Hackers use these addresses to prevent the attacked network from learning
the true source. Ingress source filtering would block these packets before
they could enter the network.
the amount of routing information that must be passed. IGPs sometimes use
a prefix, metric, tagging, or a shortest path algorithm such as that found in
the Open Shortest Path First (OSPF) protocol. The updates used by an IGP
can be small compared to the routing updates for BGP, which have the
potential of carrying many path attributes.
that has path attributes such as intra-area, inter-area, and external status.
BGP has the ability to attach many attributes to a given route. The minimum
set of path attributes that can be included in an update message is the source
of the update, called the ORIGIN attribute, and the hop information, called
the AS_PATH attribute.
OSI Reference Model. Specifically, TCP port 179 is used. The two routers
are called endpoints, BGP peers, or BGP neighbors, and their communica-
tions, which are reliable connection-oriented connections, are referred to as
sessions. When a router advertises its prefixes or routes, this router is known
as a BGP speaker. The routes that it advertises are considered valid by the